Page 1
High Voltage EL Lamp Driver for
p
_
C
S
3
5
G
S
c
sc
d
V
l
Low Noise Applications
HV857
HV857
Features
❏ Patent pending audible noise reduction
❏ Patent pending lamp aging compensation
❏ 190V
❏ Patented output timing for high efficiency
❏ Single cell lithium ion compatible
❏ 150nA shutdown current
❏ Wide input voltage range 1.8V to 5.0V
❏ Separately adjustable lamp and converter frequencies
❏ Output voltage regulation
❏ Split supply capability
output voltage for higher brightness
PP
Applications
❏ LCD backlighting
❏ Mobile cellular phones
❏ PDAs
❏ Handheld wireless communication products
❏ Global Positioning Systems (GPS)
General Description
The Supertex HV857 is a high voltage driver designed for driving
Electroluminescent (EL) lamps of up to 5 square inches. The
input supply voltage range is from 1.8V to 5.0V. The device uses
a single inductor and a minimum number of passive components.
The nominal regulated output voltage that is applied to the EL
lamp is
the resistor on R
The HV857 has two internal oscillators, a switching MOSFET,
and a high voltage EL lamp driver. The frequency for the
switching MOSFET is set by an external resistor connected
between the R
driver frequency is set by an external resistor connected between R
connected between the LX and VDD pins or VIN for split supply
applications. A 0.003-0.1µF capacitor is connected between C
and ground. The EL lamp is connected between VA and VB.
The switching MOSFET charges the external inductor and
discharges it into the capacitor at Cs. The voltage at Cs will start
to increase. Once the voltage at Cs reaches a nominal value of
95V, the switching MOSFET is turned OFF to conserve power.
The outputs V
switching in opposite states to achieve ±95V across the EL lamp.
±95V. The chip can be enabled/disabled by connecting
to VDD/ground.
sw-osc
pin and the supply pin VDD. The EL lamp
sw-osc
pin and the VDD pin. An external inductor is
EL-osc
and VB are configured as an H bridge and are
A
s
Typical Application
ON=V
DD
OFF=0
Regulated Voltage=
VDD=
11/14/01
Supertex Inc. does not recommend the use of its products in life support applications and will not knowingly sell its products for use in such applications unless it receives an adequate "products liability
indemnification insurance agreement." Supertex does not assume responsibility for use of devices described and limits its liability to the replacement of devices determined to be defective due to
workmanship. No responsibility is assumed for possible omissions or inaccuracies. Circuitry and specifications are subject to change without notice. For the latest product specifications, refer to the
Supertex website: http://www.supertex.com. For complete liability information on all Supertex products, refer to the most current databook or to the Legal/Disclaimer page on the Supertex website.
Enable Signa
EL Lam
W-os
EL-o
n
HV857M
1
Page 2
Electrical Characteristics
DC Characteristics (Over recommended operating conditions unless otherwise specified, T
Symbol Parameter Min Typ Max Units Conditions
R
DS(on)
V
Cs
VA – V
I
DDQ
I
DD
I
IN
V
Cs
f
EL
f
SW
D Switching transistor duty cycle 88 % See Figure 1.
* The inductor used is a 220µH Murata inductor, max DC resistance of 8.4Ω, part # LQH32CN221K21.
On-resistance of switching transistor 6.0 Ω I=100mA
Max. output regulation voltage 85 95 105 V VDD=1.8V to 5.0V
Peak to Peak output voltage 170 190 210 V VDD=1.8V to 5.0V
B
Quiescent VDD supply current 150 nA R
Input current going into the VDD pin 150 µAVDD=1.8V to 5.0V. See Figure 1.
Input current including inductor current 20 25 mA See Figure 1.*
Output voltage on V
Cs
84 V See Figure 1.
EL lamp frequency 205 240 275 Hz See Figure 1.
Switching transistor frequency 80 KHz See Figure 1.
SW-OSC
=25°C)
A
=Low
Recommended Operating Conditions
Symbol Parameter Min Typ Max Units Conditions
V
DD
f
EL
T
A
Supply voltage 1.8 5.0 V
Output drive frequency 1 KHz
Operating temperature -40 85 °C
HV857
Enable/Disable Function Table
Symbol Parameter Min Typ Max Units Conditions
EN-L Logic input low voltage 0 0.2 V VDD=1.8V to 5.0V
EN-H Logic input high voltage VDD-0.2 V
Absolute Maximum Ratings*
Supply Voltage, V
DD
-0.5V to +6.5V
Pin Configuration
DD
VVDD=1.8V to 5.0V
Operating Temperature Range -40° to +85°C
Storage Temperature Range -65°C to +150°C
MSOP-8 Power Dissipation 300mW
Output voltage, V
Note:
*Absolute Maximum Ratings are those values beyond which damage to the device
may occur. Functional operation under these conditions is not implied. Continuous operation of the device at the absolute rating level may affect device reliability.
All voltages are referenced to device ground.
CS
-0.5 to +120V
V
DD
1
R
SW
2
MSOP-8
R
Gnd L
EL
3
4
Ordering Information
Package Options
Device MSOP-8 Die
HV857 HV857MG* HV857X
* Product supplied on 2500 piece carrier tape reels.
Top View
V
A
8
V
7
B
C
6
S
5
X
2
Page 3
Block Diagram
F
_
3.3nF
00V
3
5
G
S
c
sc
d
S
0
µ
5
0
µ
0M
l
)
0K
p
V
DD
R
SW
GND
Rel
Switch
Osc
Disable
HV857
L
X
C
S
Q
V
+
C
_
Vref
Vsen
High
Voltage
Q
A
Level
V
DD
Tr ans-
lators
Q
EL
Osc
Q
V
B
Figure 1: Typical Application/Test Circuit
ON=V
DD
OFF=0
Typical Performance
Device Lamp Size V
HV857MG 3.0 in
2
1.
Enable Signa
=
W-os
EL-o
2.
n
HV857M
LX=220µH Murata (LQH32CN221K21
SB01-15=150V Sanyo Diode
IN
I
IN
3.3V 20mA 84V 240Hz 6.0ft-lm
V
CS
f
EL
Equivalent to 3.0in lam
2.
10n
B01-1
22
1
Brightness
3
Page 4
HV857
Iin vs Vin
13
15
17
19
21
23
25
1.5 2.5 3.5 4.5 5.5
Vin (V)
Iin vs Vcs
14
16
18
20
22
24
55 65 75 85 95
Vcs (V)
Typical Performance Curves for Figure 1 (EL Lamp=3.0in
Vcs vs Vin
95
85
V)
75
CS (
V
65
55
1.5 2.5 3.5 4.5 5.5
Vin (V)
Brightness vs Vin
7
)
6
5
(ft-lm
4
3
2
Brightness
1
1.5 2.5 3.5 4.5 5.5
Vin (V)
mA)
(
lin
mA)
(
lin
2
, VDD=3.0V)
100
90
80
70
60
(V)
CS
50
mA), V
40
(
lin
30
20
10
0
100 200 300 400 500 600
150 250 350 450 550
Iin, Vcs, Brightness vs Inductor Value
Brightness
Iin
lin
Inductor Value (µH)
4
Vcs
7
6
5
)
4
3
Brightness
2
1
0
(ft-lm
Page 5
External Component Description
External Component Selection Guide Line
Diode Fast reverse recovery diode, 150V Sanyo SB01-15 or equivalent.
Cs Capacitor 0.003µF to 0.1µF, 100V capacitor to GND is used to store the energy transferred from the inductor.
HV857
R
EL-osc
The EL lamp frequency is controlled via an external REL resistor connected between R
device. The lamp frequency increases as R
of current drawn from the battery will increase and the output voltage V
decreases. As the EL lamp frequency increases, the amount
EL
will decrease. The color of the EL
CS
and VDD of the
EL-osc
lamp is dependent upon its frequency.
A 2MΩ resistor would provide lamp frequency of 205 to 275Hz. Decreasing the R
by a factor of 2 will
EL-osc
increase the lamp frequency by a factor of 2.
R
SW-osc
The switching frequency of the converter is controlled via an external resistor, RSW between R
SW-osc
and V
DD
of the device. The switching frequency increases as RSW decreases. With a given inductor, as the switching
frequency increases, the amount of current drawn from the battery will decrease and the output voltage, VCS,
will also decrease.
Lx Inductor The inductor Lx is used to boost the low input voltage by inductive flyback. When the internal switch is on,
the inductor is being charged. When the internal switch is off, the charge stored in the inductor will be
transferred to the high voltage capacitor C
. The energy stored in the capacitor is connected to the internal
S
H-bridge and therefore to the EL lamp. In general, smaller value inductors, which can handle more current,
are more suitable to drive larger size lamps. As the inductor value decreases, the switching frequency of the
inductor (controlled by R
) should be increased to avoid saturation.
SW
220µH Murata (LQH32CN221) inductors with 8.4Ω series DC resistance is typically recommended. For
inductors with thesame inductance value but with lower series DC resistance, lower RSW value is needed to
prevent high current draw and inductor saturation.
Lamp As the EL lamp size increases, more current will be drawn from the battery to maintain high voltage across
the EL lamp. The input power, (V
x IIN), will also increase. If the input power is greater than the power
IN
dissipation of the package (300mW), an external resistor in series with one side of the lamp is recommended
to help reduce the package power dissipation.
5
Page 6
HV857
p
_
3
5
G
V
S
c
sc
d
S
V
l
Split Supply Configuration
The HV857 can also be used for handheld devices operating
from a battery where a regulated voltage is available. This is
shown in Figure 2. The regulated voltage can be used to run
the internal logic of the HV857. The amount of current necessary to run the internal logic is 150µA Max at a V
Therefore, the regulated voltage could easily provide the
current without being loaded down.
of 3.0V.
DD
Enable/Disable Configuration
The HV857 can be easily enabled and disabled via a logic control
signal on the R
The control signal can be from a microprocessor. RSW and R
are typically very high values. Therefore, only 10’s of microamperes will be drawn from the logic signal when it is at a logic high
(enable) state. When the microprocessor signal is high the
device is enabled and when the signal is low, it is disabled.
and REL resistors as shown in Figure 2 below.
SW
Figure 2: Split Supply and Enable/Disable Configuration
ON=V
DD
OFF=0
Regulated Voltage=
nable Signa
W-os
EL
EL Lam
attery Voltage=
EL-o
n
HV857M
11/14/01rev.10
1235 Bordeaux Drive, Sunnyvale, CA 94089
©2001 Supertex Inc. All rights reserved. Unauthorized use or reproduction prohibited.
6
TEL: (408) 744-0100 • FAX: (408) 222-4895
www.supertex.com
Page 7
HV857 Application Note
p
3
5
G
SW-osc
osc
d
S
V
5
0
µ
HV857
Application Note
AN-H43
HV857 EL Lamp Driver Circuits for Low Audible Noise or
High Brightness Applications
by Roshanak Aflatouni, Applications Engineer
This Application Note describes the method (patent pending) to
reduce the audible noise generated by an EL (Electroluminescent) lamp used in mobile phone applications.
This Application Note also provides example circuits as a guideline for applications with different lamp sizes, input voltages, and
brightness requirements.
For additional assistance in designing EL driver circuits, please
refer to Application Notes AN-H33 (effect of external components on performance of Supertex EL drivers), Lamp Driver
Circuits.
Figure 1: Typical Application Circuit
ON=V
OFF=0
DD
Enable Signal
When constructing and testing one of the driver circuits listed
below, keep in mind that results may differ from those given due
to lamp characteristics and component tolerance.
When making component changes for circuit optimization, always remove supply voltages first. After making adjustments,
bring up the supply voltage slowly starting from the minimum
required device input voltage while monitoring input current. A
sharp rise in current usually indicates a saturated inductor. Use
a higher current rated inductor, a higher value inductor, or
increase conversion frequency by lowering R
ries R
SW-OSC
value.
Lam
-
.
n
B01-1
HV857M
Sanyo Diode SB01-15CP
11/27/01
Supertex Inc. does not recommend the use of its products in life support applications and will not knowingly sell its products for use in such applications unless it receives an adequate "products liability
indemnification insurance agreement." Supertex does not assume responsibility for use of devices described and limits its liability to the replacement of devices determined to be defective due to
workmanship. No responsibility is assumed for possible omissions or inaccuracies. Circuitry and specifications are subject to change without notice. For the latest product specifications, refer to the
Supertex website: http://www.supertex.com. For complete liability information on all Supertex products, refer to the most current databook or to the Legal/Disclaimer page on the Supertex website.
7
Page 8
HV857 Application Note
Mobile Phone Circuit for Audible Noise Reduction:
1
The following table provides EL lamp audible noise and brightness for circuits which were designed based on typical EL lamp sizes for
Mobile phone applications. See Figure 1, Table 3.
Table 1
tiucriC
ni6.2
ni6.2
1
2
Note: 1. All values are nominal.
ni6.2
ni6.2
2
ni6.2
n7.1
ni7.1
ni7.1
ni7.1
ni7.1
+eziSpmaL
RseireS
2
K0+ABd1.5390.87.72
2
K52+ABd0.2339.67.32Am3.32
2
K05+ABd2.9200.51.71Am5.32
2
K57+ABd7.6238.31.31Am6.22
K001+ABd3.3208.265.9Am3.12
2
ni7.1
K0+ABd0.2309.695.32
2
K52+ABd3.8253.637.12Am5.51
2
K05+ABd0.6227.555.91Am6.61
2
K57+ABd4.4258.406.61Am9.61
2
K59+ABd9.2202.453.41Am5.61
2
K021+ABd0.1224.396.11Am6.51
elbiduA
esioN
ml-tfm/dC
ssenthgirBpmaLegatloVylppuS
2
V
DD
V0.3V0.3
V0.3V0.3
ylppuSxL
V
NI
tnerruC
Am6.02
Am4.31
pmaL
ycneuqerF
zH052
zH052
How to Minimize EL Lamp
Audible Noise:
The EL lamp, when lit, generates an audible noise. This is due
to EL lamp construction which creates a major problem for
applications where the EL lamp can be close to the ear such as
cellular phones. The noisiest waveform is a square wave and the
quietest waveform has been assumed to be a sine wave.
After extensive research, Supertex has developed a waveform
that is quieter than a sine wave. The waveform takes the shape
of approximately 2RC time constants for rising and 2RC time
constants for falling, where the C is the capacitance of the lamp
and R is the external resistor used in series with one side of the
lamp. This waveform has been proven to generate less noise
than a sine wave.
The audible noise from the EL lamp can be set at a desired level
based on the series resistor value used with the lamp. We have
chosen two commonly used lamp sizes for the mobile phones to
demonstrate the effect of series resistor on the audible noise
generated by the EL lamp. It is important to note that use of this
resistor will reduce the voltage across the lamp. Reduction of
voltage across the lamp will also has another effect on the overall
performance of the Supertex EL drivers, age compensation
(patent pending). This addresses a very important issue. EL
lamp life is an important design concern to mobile phone
manufacturers.
As an EL lamp ages, its brightness is reduced and its capacitance
is diminished. By using the RC model to reduce the audible noise
generated by an EL lamp, the voltage across the lamp will
increase as its capacitance diminishes. Hence the increase in
voltage will compensate for the reduction of the brightness. As a
result, it will extend an EL lamp’s half-life (half the original
brightness).
Effect of Series Resistor on EL
Lamp Audible Noise and
Brightness:
Increasing the value of the series resistor with the lamp will
reduce the audible noise of an EL lamp as well as its brightness.
This is due to the fact that the output voltage across the lamp will
be reduced and the output waveform will have rounder edges.
8
Page 9
Circuit 1
Lamp Noise vs. Series R (2.6in2 EL Lamp)
40
35
30
25
20
15
Lamp Noise (dB)
10
020406080100 120 140 160
Series R (KΩ )
Brightness vs. Series R (2.6in2 EL Lamp)
)
30
2
25
20
15
10
5
0
Brightness (cd/m
020406080100 120 140 160
Series R (KΩ )
HV857 Application Note
Circuit 2
Lamp Noise vs. Series R (1.7in2 EL Lamp)
40
35
30
25
20
15
Lamp Noise (dB)
10
020406080100 120 140 160
Series R (KΩ)
Brightness vs. Series R (1.7in2 EL Lamp)
25
)
2
20
15
10
5
Brightness (cd/m
0
020406080100 120 140 160
Series R (KΩ)
9
Page 10
HV857 Application Note
Typical HV857 Output waveform Before and After Noise Reduction:
The following are actual scope pictures, which show the differential output waveform across the lamp, audible noise, and lamp light output
for circuits 1 and 2.
Circuit 1
Series R=0Ω
100V/div
50mV/div
200mV/div
100V/div
Differential Output Waveform
across the lamp
Audible Noise
Light Output
1ms/div
Series R=65KΩ
Differential Output Waveform
across the lamp
50mV/div
200mV/div
Audible Noise
Light Output
1ms/div
10
Page 11
Circuit 2
HV857 Application Note
Series R=0Ω
100V/div
20mV/div
200mV/div
100V/div
Differential Output Waveform
across the lamp
Audible Noise
Light Output
1ms/div
Series R=55KΩ
Differential Output Waveform
across the lamp
20mV/div
200mV/div
Audible Noise
Light Output
1ms/div
11
Page 12
HV857 Application Note
Audible Noise Measurement Setup:
The following setup was used to collect EL lamp audible noise data. An Oscilloscope/Spectrum analyzer was used to observe the
differential output waveform, audible noise level (in mV), and light output (in mV) of the EL lamp. The EL lamp is placed in the anechoic
chamber and a condenser microphone is placed 10mm away from the surface of the EL lamp.
Driver Measurement Test Setup
Oscilloscope/Spectrum
Analyzer
10:1 probes
Signal Conditioner
Soundproof Anechoic Chamber
EL Lamp
Opto-acoustic
Probe
A-weighting
filter
NC
Headphones
EL
Driver
-+
DC
Supply
Drawing not to scale
Pneumatic
Supports
10mm
Scaling
Scaling
Opto-acoustic probe is battery powered
to minimize electrical noise.
Low pass
filter
NC
12
Page 13
HV857 Application Note
Circuit Selector Guide for Non Audible Noise Sensitive Applications:
(Handheld products, PDAs, GPS, 2-way pagers, MP3)
No series resistor is used for the following circuits (R=0Ω). Also see Figure 1 and Table 3.
Table 2
tiucriC
3ni3.1
4ni7.1
5ni7.1
6ni39.0
7ni1.3
8ni0.4
pmaL
eziS
2
2
2
2
2
2
pmaL
ssenthgirB
ml-tfm/dC
2
V
DD
83.901.23V3.3V3.3Am9.21p-pV081zH753
44.4
84.4
0.21
2.31
2.51
13.51
6.14
3.54
V0.3
V0.3
47.715.62V0.3V0.3Am3.8p-pV571zH052
48.778.62V0.5V0.5Am9.71p-pV481zH052
05.77.52V0.3V0.3Am8.52p-pV061zH052
egatloVylppuS
V
NI
V2.3
V2.4
V2.3
V2.4
xL
ylppuS
tnerruC
Am4.7
Am7.5
Am7.32
Am9.02
tuptuO
egatloV
p-pV281
p-pV681
p-pV861
p-pV871
pmaL
ycneuqerF
zH061
zH574
1
9ni2.5
2
77.443.61V3.3V3.3Am2.12p-pV861zH061
Note: 1. All values are nominal. Lamp brightness and current draw can vary by type and manufacturer.
External components used for Circuits 1 to 9:
The following table provides the value for external components used in Figure 1. The manufacturer and part number for the inductor is
also provided. If other value inductors are used, the circuit will need to be reoptimized.
Table 3
tiucriC
1Hµ022
2Hµ022
3Hµ022
4Hµ022
5Hµ022
6Hµ022
7Hµ022
8Hµ022
9Hµ022
rotcudnIxL
R
eulaV
,rerutcafunaM
.oN.traP
,ataRuM
12K122NC23HQL
ataRuM
12K122NC23HQL
,ataRuM
12K122NC23HQL
,ataRuM
12K122NC23HQL
,ataRuM
12K122NC23HQL
,ataRuM
12K122NC23HQL
,ataRuM
12K122NC23HQL
,ataRuM
10K122NM34HQL
,ataRuM
10K122NM34HQL
CSO-WS
K065M0.2Fn3.3OPN
K065M0.2Fn3.3OPN
K065M5.1Fn3.3OPN
K033M3.3Fn3.3OPN
K065M0.1Fn3.3OPN
K065M0.2Fn3.3OPN
K065M0.2Fn3.3OPN
K065M0.2Fn3.3OPN
K065M3.3Fn3.3OPN
R
CSO-LE
C
S
eulaVepyT
roticapaC
13
Page 14
HV857 Application Note
LX Inductor Selection:
Different inductor values and/or from different manufacturers
can be used in place of what is shown. However, the circuit will
need to be reoptimized by changing the R
R
value needs to be used for inductors with lower series
SW-OSC
resistance. Lower amount of current will be drawn when using
larger value inductors. But, for the same R
amount of energy will be transferred due to the higher series
resistance of a larger value inductor. Hence, when larger value
inductors with higher series resistance are used, the R
value needs to be increased. It is very important to make a note
of the saturation current of the inductor. If the saturation current
of the inductor is lower than what the circuit/application requires,
the inductor and/or IC will be damaged.
value. Smaller
SW-OSC
value, a lower
SW-OSC
SW-OSC
CS Capacitor Selection:
Different CS Capacitor types and value can be used in place of
what is shown in circuits 1 to 9. However, the use of a different
Capacitor type will generate audible noise due to the piezo
C
S
electric effect of materials used for their structure (such as X7R
and 5YU capacitors).
A different value capacitor can be used. A larger value C
Capacitor (10nF) is recommended to be used for larger EL lamps
and/or larger input voltage range. A smaller value C
can be used as long as the over all efficiency of the circuit is not
decreased. When using a smaller value C
Capacitor, the circuit
S
will need to be reoptimized by using a smaller R
Capacitor
S
SW-OSC
value.
S
©2001 Supertex Inc. All rights reserved. Unauthorized use or reproduction prohibited.
14
11/27/01AppNote.rev.3
1235 Bordeaux Drive, Sunnyvale, CA 94089
TEL: (408) 744-0100 • FAX: (408) 222-4895
www.supertex.com
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